Writing implement with thermochromic coloring color-memory composition

ABSTRACT

A writing implement with a thermochromic coloring color-memory composition which comprises a homogeneous solubilized mixture of (A) an electron donative coloring organic compound, (B) an electron accepting compound and (C) a reaction medium which controls color reactions of the components (A) and (B), wherein a complete decoloring temperature (T 4 ) of the thermochromic coloring color-memory composition is 50° C. or higher and a coloring starting temperature (T 2 ) of thermochromic coloring color-memory composition is 10° C. or lower regarding the color density-temperature curve, and the thermochromic coloring color-memory composition has color-memory ability at the ordinary temperature range.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.10/845,128, filed May 14, 2004 (now allowed); which claims priority fromJapanese Application No. P.2003-138990, filed May 16, 2003, and JapaneseApplication No. P.2003-319039, filed Sep. 10, 2003. The entiredisclosures of the prior applications are considered part of thedisclosure of the present Application, and are hereby incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to a thermochromic coloring color-memorycomposition and a thermochromic coloring color-memory microcapsulepigment containing the same. More illustratively, it relates to athermochromic coloring color-memory composition which displaysreversible discoloration between coloring and decoloring by showing alarge hysteresis characteristic based on a change in temperature andkeeps either of the colored state and decolored state alternately andreversibly even after removal of application of the heat or coldrequired for the discoloration, and to a thermochromic coloringcolor-memory microcapsule pigment containing the same.

BACKGROUND ART

Regarding such a type of thermochromic coloring color-memory material,the applicant has already proposed (for example, see Patent Reference1).

In a conventional reversible thermal discoloration material, itdiscolors bordering before and after a discoloration temperature, onlyone specified state of both states before and after discoloration existsat the ordinary temperature region, and the other state is maintainedwhile a heat or cold necessary for expressing the state is applied butreturns to the state of ordinary temperature region when application ofthe heat or cold is removed, but in comparison with such a type, theaforementioned thermochromic coloring color-memory material canselectively maintain either of the color of lower side than thediscoloration temperature and the color of higher side than that, at theordinary temperature region and can alternately maintain the color byapplying a heat or cold as occasion demands, so that it has been appliedto various fields such as the fields of thermo-sensitive recordingmaterials, toys, ornaments and printing.

[Patent Reference 1] U.S. Pat. No. 4,720,301

SUMMARY OF THE INVENTION

As is disclosed in the aforementioned U.S. Pat. No. 4,720,301, such akind of color-memorizing effect is expressed only in a system to which,among compounds selected from esters that control the color reaction, aspecified compound is applied as a constituting component.

The invention contemplates further searching for compounds which can beused as a reaction medium for expressing the aforementionedcolor-memorizing effect and thereby improving degree of freedom for theselection of reaction medium and further increasing availability of sucha kind of thermochromic coloring color-memory material.

The present inventors have accomplished the invention by finding that athermal discoloration characteristic having a large maximum hysteresiswidth (ΔH) is exerted and an effective color-memorizing effect isexpressed in a system to which an ester compound comprising an alcoholcompound having 2 aromatic rings in the molecule and a saturated orunsaturated fatty acid having 4 or more carbon atoms is applied as thereaction medium of color reaction.

A requirement of the invention is a thermochromic coloring color-memorycomposition which comprises a homogeneous solubilized mixture of (A) anelectron donative coloring organic compound, (B) an electron acceptingcompound and (C) an ester compound represented by the following formula(1) as a reaction medium which controls color reactions of theaforementioned (A) and (B).

In the formula, R represents an alkyl group or alkenyl group, having 4or more carbon atoms.

Its another requirement is that the aforementioned (B) electronaccepting compound is a compound which has at least 3 or more benzenerings and also has a phenolic hydroxyl group, and has a molecular weightof 250 or more, or a compound which has the phenolic hydroxyl group,represented by the following formula (2).

In the formula, R represents an alkyl group having from 1 to 8 carbonatoms.

Its another requirement is that the present composition has acolor-memory ability at the ordinary temperature range, wherein it showsa maximum hysteresis width (ΔH) of from 40° C. to 70° C. regarding acolor density-temperature curve, and the complete decoloring temperature(T₄) is 40° C. or higher and the coloring starting temperature (T₂) is20° C. or lower regarding the color density-temperature curve.

Still another requirement is a thermochromic coloring color-memorymicrocapsule pigment which comprises the aforementioned thermochromiccoloring color-memory composition.

Based on the use of an ester compound comprising an alcohol compoundhaving 2 aromatic rings in the molecule and a saturated or unsaturatedfatty acid having 4 or more carbon atoms, the invention can generatereversible discoloration of coloring and decoloring showing a broadmaximum hysteresis width (ΔH) regarding a color density-temperaturecurve, can alternately memorize and keep both of the color of lowtemperature side and the color of high temperature side compared to thediscoloration temperature, and can effectively express a characteristicin that either of the colors can be reversibly reproduced, memorized andmaintained by applying a heat or cold as occasion demands, so that itrenders possible provision of a thermochromic coloring color-memorycomposition and a thermochromic coloring color-memory microcapsulepigment containing the same, which, in comparison with the conventionalester compound-formulated system, are rich in practicality and have theapplicability to various fields such as of heat sensitive materials,ornaments, toys and training elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph describing hysteresis characteristics of thethermochromic coloring color-memory composition of the invention incolor density-temperature curves.

FIG. 2 is a graph describing hysteresis characteristics of thethermochromic coloring color-memory composition of the invention incolor density-temperature curves.

In Figs., sign T₁ is a complete coloring temperature, sign T₂ is acoloring starting temperature, sign T₃ is a decoloring startingtemperature, sign T₄ is a complete decoloring temperature, sign ΔH is amaximum hysteresis width.

DETAILED DESCRIPTION OF THE INVENTION

Hysteresis characteristic in a color density-temperature curve of thethermochromic coloring color-memory composition of the invention isdescribed in the following based on the graph of FIG. 1.

In FIG. 1, the color density is plotted as ordinate and the temperatureas abscissa. Change in the color density due to temperature changeprogresses along the arrow. In this case, A is a point showing thedensity at a minimum temperature T₄ which reaches a completely decoloredstate (to be referred to as complete decoloring temperature hereinafter), B is a point showing the density at a maximum temperature T₃which can maintain a completely colored state (to be referred to asdecoloring starting temperature herein after), C is a point showing thedensity at a minimum temperature T₂ which can maintain a completelydecolored state (to be referred to as coloring starting temperatureherein after), and D is a point showing the density at a maximumtemperature T₁ which reaches a completely colored state (to be referredto as complete coloring temperature herein after).

The discoloration temperature region is a temperature region between theaforementioned T₁ and T₄, wherein two phases of the colored state anddecolored state can coexist, and the temperature region between T₂ andT₃, as the region having a large difference in the color density, is asubstantial discoloration temperature region (two phase retentionregion).

Also, length of the line segment EF is a measure showing contrast ofdiscoloration, and length of the line segment HG is a temperature widthshowing the degree of hysteresis (to be referred to as maximumhysteresis width ΔH hereinafter), wherein larger ΔH value facilitateskeeping of each state of before and after discoloration.

According to the tests carried out by the inventors, the ΔH value whichcan keep each state of before and after discoloration is within therange of from 40° C. to 70° C., preferably from 50 to 70° C., morepreferably from 60 to 70° C.

Also, regarding a temperature to be subjected to the practical use inwhich the aforementioned two phases of colored state and decolored stateare substantially maintained, namely the temperature width between T₃and T₂ including T_(A), a range of from 20° C. or more to less than 60°C. is effective.

In addition, in order to allow only one specified state of both statesbefore and after discoloration to exist at the ordinary temperaturerange, the complete decoloring temperature (T₄) is 40° C. or higher,preferably 45° C. or higher and more preferably 50° C. or higher, andthe coloring starting temperature (T₂) is 20° C. or lower, preferably10° C. or lower and more preferably 0° C. or lower.

In this connection, a Δt value as the difference between T₄ and T₃, oras the difference between T₂ and T₁, is a measure for showing sharpnessof the discoloration.

In addition, the ordinary temperature range indicates the temperatureassumed to be experienced under usual indoor conditions.

Though the constituting component ratio of the components (A), (B) and(C) of the invention is influenced by the concentration, discolorationtemperature, discoloration mode and kind of each component, thecomponent ratio from which generally desired characteristics can beobtained is component (B) within the range of from 0.1 to 50, preferablyfrom 0.5 to 20, and component (C) within the range of from 1 to 800,preferably from 5 to 200, based on component (A) 1 (each of theaforementioned ratios is weight part(s)).

Also, each component may be a mixture of two or more species, andadditives such as an antioxidant, an ultraviolet ray absorbent, aninfrared ray absorbent and a solubilizing agent can be added theretowithin such a range that its function is not spoiled.

Compounds of the components (A), (B) and (C) are illustrativelyexemplified in the following.

As the component (A) of the invention, namely an electron donativecoloring organic compound, conventionally known compounds such asdiphenylmethane phthalides, phenylindolyl phthalides, indolylphthalides, diphenylmethane azaphthalides, phenylindolyl azaphthalides,fluorans, styrylquinolines and diazarhodamine lactones can beexemplified, and examples of these compounds are shown below.

Their examples include

-   3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide,-   3-(4-diethylamunophenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide,-   3,3-bis(1-n-butyl-2-methylindol-3-yl)phthalide,-   3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide,-   3-[2-ethoxy-4-(N-ethylanilino)phenyl]-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide,    3,6-diphenylaminofluoran,-   3,6-dimethoxyfluoran, 3,6-di-n-butoxyfluoran,-   2-methyl-6-(N-ethyl-N-p-tolylamino)fluoran,-   3-chloro-6-cyclohexylaminofluoran,-   2-methyl-6-cyclohexylaminofluoran,-   2-(2-chloroanilino)-6-di-n-butylaminofluoran,-   2-(3-trifluoromethylanilino)-6-diethylaminofluoran,-   2-(N-methylanilino)-6-(N-ethyl-N-p-tolylamino)fluoran,-   1,3-dimethyl-6-diethylaminofluoran,-   2-chloro-3-methyl-6-diethylaminofluoran,-   2-anilino-3-methyl-6-diethylaminofluoran,-   2-anilino-3-methyl-6-di-n-butylaminofluoran,-   2-xylidino-3-methyl-6-diethylaminofluoran,-   1,2-benz-6-diethylaminofluoran,-   1,2-benz-6-(N-ethyl-N-isobutylamino)fluoran,-   1,2-benz-6-(N-ethyl-N-isoamylamino)fluoran,-   2-(3-methoxy-4-dodecoxystyryl)quinoline,    spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one,    2-(diethylamino)-8-(diethylamino)-4-methyl-,-   spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one,-   2-(di-n-butylamino)-8-(di-n-butylamino)-4-methyl-,-   spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one,-   2-(di-n-butylamino)-8-(diethylamino)-4-methyl-,-   spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one,-   2-(di-n-butylamino)-8-(N-ethyl-N-1-amylamino)-4-methyl-,-   spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one,-   2-(di-n-butylamino)-8-(di-n-butylamino)-4-phenyl,-   3-(2-methoxy-4-dimethylaminophenyl)-3-(1-butyl-2-methylindol-3-yl)    4,5,6,7-tetrachlorophthalide,-   3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4,5,6,7-tetrachlorophthalide,    and-   3-(2-ethoxy-4-diethylaminophenyl)-3-(1-pentyl-2-methylindol-3-yl)-4,5,6,7-tetrachlorophthalide.

Also can be exemplified are pyridine, quinazoline and bisquinazolinecompounds which are effective in expressing development of fluorescentyellow to red colors.

As the electron accepting compound of component (B), a group ofcompounds which have active proton, a group of pseudo-acidic compounds(a group of compounds which are not acid but cause color development ofthe component (A) by acting as acid in the composition) and a group ofcompounds which have electron voids can be cited.

Examples of the compound having active proton as compounds havingphenolic hydroxyl group include from monophenols to polyphenols, theirderivatives which have substituent groups such as alkyl group, arylgroup, acyl group, alkoxycarbonyl group, carboxy group, esters thereof,amido group and halogen group, and phenol-aldehyde condensed resins suchas of bis type and tris type phenols.

In addition, they may also be metal salts of the aforementionedcompounds having phenolic hydroxyl group.

Illustrative examples are listed below.

Phenol, o-cresol, tertiary butylcatechol, nonylphenol, n-octylphenol,n-dodecylphenol, n-stearylphenol, p-chlorophenol, p-bromophenol,o-phenylphenol, n-butyl p-hydroxybenzoate, n-octyl p-hydroxybenzoate,resorcin, dodecyl gallate, 2,2-bis(4′-hydroxyphenyl)propane,

-   4,4-dihydroxydiphenylsulfone,-   1,1-bis(4′-hydroxyphenyl)ethane,-   2,2-bis(4′-hydroxy-3-methylphenyl)propane,-   bis(4-hydroxyphenyl) sulfide,-   1-phenyl-1,1-bis(4′-hydroxyphenyl)ethane,-   1,1-bis(4′-hydroxyphenyl)-3-methylbutane,-   1,1-bis(4′-hydroxyphenyl)-2-methylpropane,-   1,1-bis(4′-hydroxyphenyl)-n-hexane,-   1,1-bis(4′-hydroxyphenyl)-n-heptane,-   1,1-bis(4′-hydroxyphenyl)-n-octane,-   1,1-bis(4′-hydroxyphenyl)-n-nonane,-   1,1-bis(4′-hydroxyphenyl)-n-decane,-   1,1-bis(4′-hydroxyphenyl)-n-dodecane,-   2,2-bis(4′-hydroxyphenyl)butane,-   2,2-bis(4′-hydroxyphenyl)ethyl propionate,-   2,2-bis(4′-hydroxyphenyl)-4-methylpentane,-   2,2-bis(4′-hydroxyphenyl)hexafluoropropane,-   2,2-bis(4′-hydroxyphenyl)-n-heptane and-   2,2-bis(4′-hydroxyphenyl)-n-nonane.

In this connection, discoloration sensitivity in changing from adecolored state to a colored state can be sharpened when a compoundhaving at least 3 benzene rings and also having a molecular weight of250 or more, preferably from 250 to 500, or the phenolic hydroxylgroup-containing compound represented by the formula (2) is used as theaforementioned compound having phenolic hydroxyl group. Illustratively,in the discoloration behavior when the temperature showing a completelydecolored state (T₄) reaches the temperature showing a completelycolored state (T₁) via the temperature at which color development starts(T₂) as shown in FIG. 2, the temperature at which color developmentstarts (T₂) does not show a behavior of shifting to the high temperatureside and thereby gradually developing color, but temperature differencebetween the temperature at which color development starts (T₂) and thetemperature showing a completely colored state (T₁) becomes small asshown in FIG. 1, so that it becomes apt to show the behavior of sharplychanging from the decolored state to the colored state.

Examples of the aforementioned compound having at least 3 benzene ringsand also having a molecular weight of 250 or more include4,4′,4″-methylidenetrisphenol,

-   2,6-bis[(2-hydroxy-5-methylphenol)methyl]-4-methylphenol,-   4,4′-[1-[4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl]ethylidene]bisphenol,-   4,4′,4″-methylidenetris[2-methylphenol],-   4,4′-[(2-hydroxyphenyl)methylene]bis[2,3,6-triphenyl-phenol],-   2,2-methylenebis[6-[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenol],-   2,4,6-tris(4-hydroxyphenylmethyl)1,3-benzenediol,-   4,4′,4″-ethylidenetrisphenol,-   4,4′-[(4-hydroxyphenyl)methylene]bis[2-methylphenol],-   4,4′-[(4-hydroxyphenyl)methylene]bis[2,6-dimethylphenol],-   4,4′-[(4-hydroxyphenyl)methylene]bis[2-methylphenol],-   4,4′-[(4-hydroxyphenyl)methylene]bis[2,6-dimethylphenol],-   4,4′-[(4-hydroxy-3-methoxyphenyl)methylene]bis[2,6-dimethylphenol],-   2,4-bis[(5-methyl-2-hydroxyphenyl)methyl]-6-cyclohexylphenol,-   4,4′-[1-[4-[1-(4-hydroxy-3-methylphenyl)-1-methylethyl]-phenyl]ethylidene]bis[2-methylphenol],-   4,4′-[(4-hydroxyphenyl)methylene]bis[2-cyclohexyl-5-methylphenol],-   4,6-bis[(4-hydroxyphenyl)methyl]1,3-benzenediol,-   4,4′-[(3,4-dihydroxyphenyl)methylene]bis[2,6-dimethylphenol],-   4,4′-(1-phenylethylidene)bisphenol,-   5,5′-(1-methylethylidene)bis[1-phenyl-2-ol],-   4,4′,4″-methylidenetrisphenol,-   4,4′-[1-[4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl]-ethylidene]bisphenol,-   4,4′-(phenylmethylene)bisphenol,-   4,4′-[1,4-phenylenebis(1-methylethylidene)]bis[2-methylphenol], and-   5,5′-(1,1-cyclohexylidene)bis[1-biphenyl-2-ol].

Examples of the aforementioned phenolic hydroxyl group-containingcompound represented by general formula (2) includebis(3-methyl-4-hydroxyphenyl)sulfide,

-   bis(3,5-dimethyl-4-hydroxyphenyl)sulfide,-   bis(3-ethyl-4-hydroxyphenyl)sulfide,-   bis(3,5-diethyl-4-hydroxyphenyl)sulfide,-   bis(3-propyl-4-hydroxyphenyl)sulfide,-   bis(3,5-dipropyl-4-hydroxyphenyl)sulfide,-   bis(3-t-butyl-4-hydroxyphenyl)sulfide,-   bis(3,5-t-butyl-4-hydroxyphenyl)sulfide,-   bis(3-pentyl-4-hydroxyphenyl)sulfide,-   bis(3-hexyl-4-hydroxyphenyl)sulfide,-   bis(3-heptyl-4-hydroxyphenyl)sulfide and-   bis(5-octyl-2-hydroxyphenyl)sulfide.

Though the aforementioned compound having phenolic hydroxyl group canexpress most effective thermal discoloration characteristics, it may bea compound selected from aromatic carboxylic acids and aliphaticcarboxylic acids having from 2 to 5 carbon atoms, carboxylic acid metalsalts, acidic phosphoric acid esters and metal salts thereof,1,2,3-triazole and derivatives thereof.

Next, the ester compound of component (C) is illustratively exemplified.

The ester compound to be used in the invention is an ester compoundconstituted from an alcohol compound having 2 aromatic rings in themolecule and a saturated or unsaturated fatty acid, having 4 or morecarbon atoms.

The R in the formula represents an alkyl group or an alkenyl group,having 4 or more carbon atoms, but is preferably an alkyl group havingfrom 6 to 20 carbon atoms, more preferably an alkyl group having from 8to 18 carbon atoms.

Illustrative examples of the aforementioned compound (C) include4-benzyloxyphenylethyl butanoate, 4-benzyloxyphenylethyl pentanoate,4-benzyloxyphenylethyl hexanoate, 4-benzyloxyphenylethyl heptanoate,4-benzyloxyphenylethyl octanoate, 4-benzyloxyphenylethyl nonanoate,4-benzyloxyphenylethyl decanoate, 4-benzyloxyphenylethyl undecanoate,4-benzyloxyphenylethyl didecanoate, 4-benzyloxyphenylethyl tridecanoate,4-benzyloxyphenylethyl tetradecanoate, 4-benzyloxyphenylethylpentadecanoate, 4-benzyloxyphenylethyl hexadecanoate,4-benzyloxyphenylethyl heptadecanoate, 4-benzyloxyphenylethyloctadecanoate, 4-benzyloxyphenylethyl nonadecanoate,4-benzyloxyphenylethyl eicosanoate, 4-benzyloxyphenylethyl tricosanoate,4-benzyloxyphenylethyl tetracosanoate, 4-benzyloxyphenylethylpentacosanoate, 4-benzyloxyphenylethyl hexacosanoate,4-benzyloxyphenylethyl heptacosanoate, 4-benzyloxyphenylethyloctacosanoate, 4-benzyloxyphenylethyl nonacosanoate,4-benzyloxyphenylethyl triacontanoate and 4-benzyloxyphenylethylhentriacontanoate.

In addition, among the compounds mentioned as examples, particularlypreferable ones are those enumerated below and having an alkyl groupwith 8 to 14 carbon atoms: 4-benzyloxyphenylethyl octanoate,4-benzyloxyphenylethyl nonanoate, 4-benzyloxyphenylethyl decanoate,4-benzyloxyphenylethyl undecanoate, 4-benzyloxyphenylethyl dodecanoate,4-benzyloxyphenylethyl tridecanoate, 4-benzyloxyphenylethyltetradecanoate.

Since the aforementioned ester compounds can provide a broad maximumhysteresis width similar to or larger than the case of the use of theester compounds used in the conventional thermochromic coloringcolor-memory materials, they are rich in practicality and have excellentapplicability to various applications.

Though the component (C) of the invention uses the aforementioned estercompound, additives such as other esters, alcohols, carboxylic acids,ketones and amides can be added thereto as occasion demands, within sucha range that the hysteresis characteristic is not largely changed. Inthat case, it is desirable to add them in an amount of 20 or less (partsby weight) based on 100 of the ester of the invention, for effectivelyexpressing the intended color-memorizing effect.

A homogeneous solubilized mixture indicates the state that components(A), (B) and (C) are homogeneously mixed together.

The homogeneous solubilized mixture is obtained by, after mixingcomponents (A), (B) and (C), dissolving components (A) and (B) incomponent (C).

The homogenous solubilized mixture comprising the aforementioned threecomponents can form a thermochromic coloring color-memory microcapsulepigment by including the mixture in microcapsules.

The aforementioned microcapsules satisfy the practicality when theiraverage particle diameter is within the range of from 0.5 to 50 μm,preferably from 1 to 30 μm, more preferably from 1 to 20 μm.

When the aforementioned microcapsules are a system in which averagevalue of the maximum outer diameter exceeds 50 μm, they lack indispersion stability and processing suitability in blending in inks,paints or resins.

On the other hand, in the case of a system in which average value of themaximum outer diameter is 0.5 μm or less, high density coloring canhardly be obtained.

In addition, the aforementioned microcapsules are effective within therange of inclusion body/wall membrane=7/1 to 1/1 (weight ratio), andsince reduction of color density and clearness at the time of colordevelopment cannot be avoided when the ratio of inclusion body becomeslarger than the aforementioned range, it is preferably inclusionbody/wall membrane=6/1 to 1/1 (weight ratio).

Examples of the microencapsulation method include conventionally knownisocyanate system interfacial polymerization, in situ polymerizationsuch as of melamine-formalin system, submerged coat hardening, phaseseparation from aqueous solution, phase separation from organic solvent,melt dispersion cooling, air suspension coating and spray drying, whichcan be optionally selected in response to the object. In addition, themicrocapsules can be subjected to practical use by further givingdurability and modifying surface characteristics in response to theobject through the arrangement of a secondary resin coating on thesurface.

In this connection, a discoloration behavior from a color (1) to a color(2) can be effected by formulating the aforementioned thermochromiccoloring color-memory composition or thermochromic coloring color-memorymicrocapsule pigment containing the same with a general dyestuff orpigment (non-thermal discoloration type).

The aforementioned thermochromic coloring color-memory composition orthermochromic coloring color-memory microcapsule pigment containing thesame can be used as a thermochromic coloring color-memory liquidcomposition by dispersing in a vehicle containing various additiveagents as occasion demands, for such applications as a printing ink tobe used in screen printing, offset printing, process printing, gravureprinting, coater or pad application, a paint to be used in brushcoating, spray coating, electrostatic coating, electro-depositioncoating, flow coating, roller coating or dip coating, an ink for ink jetuse, an ink for use in writing or coating implements such as markingpen, ball-point pen, fountain pen and writing brush pen, and a coloringliquid for use in crayon, colors, cosmetics or fibers.

In this connection, the material of the aforementioned support is notlimited and every material is effective, and its examples include paper,synthetic paper, fiber, cloth, synthetic leather, leather, plastics,glass, pottery materials, metals, wood and stone, which may be not onlyin flat shape but also in irregular form.

In case that a non-thermal discoloration coloring layer (including animage) is formed in advance on the aforementioned support, theaforementioned coloring layer can be in-visualized by a temperaturechange, so that the changing mode can be further varied.

In addition, the aforementioned thermochromic coloring color-memorycomposition or thermochromic coloring color-memory microcapsule pigmentcontaining the same can be used as a resin composition for thermochromiccoloring color-memory molding as a form of pellet, powder or paste, bymelt-blending with a thermoplastic resin, a thermosetting resin or awax.

Various shapes of moldings such as three-dimensional moldings ofoptional shapes, films, sheets, plates, filaments, rods or pipes can beobtained using the aforementioned resin for molding use, by means ofinjection molding, extrusion molding, blow molding or cast molding.

Examples of the aforementioned additive agent include a crosslinkingagent, a curing agent, a desiccating agent, a plasticizer, a viscosityadjusting agent, a dispersing agent, an ultraviolet ray absorbent, anantioxidant, light stabilizer, a sedimentation preventing agent, alubricant, a gelling agent, an antifoaming agent, a flatting agent, apenetrating agent, a pH regulator, a foaming agent, a coupling agent, amoisture keeping agent, a fungicide, an antiseptic and an anticorrosiveagent.

Light resistance of a layered product prepared by forming a reversibleheat discoloring layer of the aforementioned liquid matter on a support,or a molded product thereof, can be improved by laminating thereon alayer containing a light stabilizer and/or a transparent metallic lusterpigment, or durability of the same can also be improved by arranging atopcoat layer thereon.

As the aforementioned transparent metallic luster pigment, a pigmentprepared by coating the surface of a core substance such as naturalmica, synthetic mica, glass piece, alumina or a piece of a transparentfilm with a metal oxide such as titanium oxide can be exemplified.

Regarding the product prepared making use of the aforementionedthermochromic coloring color-memory composition or thermochromiccoloring color-memory microcapsule pigment containing the same, itsillustrative examples include doll- or animal figured toys, hair for adoll- or animal figured toy, doll accessories such as house, furniture,clothing, hat, bag and shoes for a doll, accessory toys, stuffed dolls,painting toys, picture books for toys, puzzle toys such as a jigsawpuzzle, toy bricks, block toys, clay toys, fluid toys, tops, kites,musical instrument toys, cooking toys, gun toys, capturing toys,background toys, toys imitating vehicles, animals, plants, buildings orfood articles, clothes such as a T-shirt, a sweet shirt, a blouse, adress, a bathing suit, a raincoat and a skiwear, footwear such as shoesand shoelaces, personal effects made of cloth such as a handkerchief, atowel and a wrapping cloth, interior ornaments such as a rug, a curtain,a curtain cord, a tablecloth, a carpet, a cushion, a picture frame andan imitation flower, bedding such as bedclothes, a pillow and amattress, accessories such as a ring, a bracelet, a tiara, earrings, ahair stopper, an attaching nail, a ribbon and a scarf, stationary suchas a writing tool, a stamp, an eraser, a celluloid board, a ruler and anadhesive tape, cosmetics such as a lipstick, an eye shadow, a manicure,a hair dye, an attaching nail and a paint for attaching nail, kitchenutensils such as a glass, a plate, chopsticks, a spoon, a fork, a potand a frying pan, various printed matter such as a calendar, a label, acard, a recording material and those for forgery prevention, books suchas a picture book, and gloves, a necktie, a hat, a bag, a container forpacking use, embroidery thread, sporting goods, fishing goods, atoothbrush, a coaster, a watch, eyeglasses, lighting fixture, an airconditioner, a musical instrument, a pocket body warmer, a coldreserving agent, a photo stand, and bags and pouches of all kinds suchas a purse, as well as an umbrella, furniture, a vehicle, aconstruction, a temperature detecting indicator and training goods.

EXAMPLES

Examples of the invention are shown below, but the invention is notlimited thereto.

The method for producing a thermochromic coloring color-memorycomposition and a microcapsule pigment containing the same and themethod for measuring hysteresis characteristics of a thermochromiccoloring color-memory composition and a microcapsule pigment containingthe same based on the change in temperature, in respective examples, aredescribed in the following.

In this connection, the term “part(s)” in the following blendingexamples means part(s) by weight.

Example 1

A thermochromic coloring color-memory composition was obtained byhomogeneously and solubilizly dissolving 2.0 parts of3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalideas the component (A), 4.0 parts of 2,2-bis (4′-hydroxyphenyl)hexafluoropropane and 4.0 parts of 1,1-bis (4′-hydroxyphenyl)-n-decaneas the component (B) and 50.0 parts of 4-benzyloxyphenylethyl caprate asthe component (C).

This thermochromic coloring color-memory composition changed color fromblue to colorless.

Example 2

A thermochromic coloring color-memory microcapsule pigment suspensionwas obtained by uniformly heat-dissolving a thermochromic coloringcolor-memory composition comprising 2.0 parts of3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalideas the component (A), 8.0 parts of 1,1-bis (4′-hydroxyphenyl)-n-decaneas the component (B) and 50.0 parts of 4-benzyloxyphenylethyl palmitateas the component (C), emulsifying and dispersing a solution prepared asa wall membrane material by mixing 30.0 parts of an aromatic polyvalentisocyanate prepolymer with 40.0 parts of a co-solvent such thatmicro-droplets were formed in 8% polyvinyl alcohol aqueous solution,continuing the stirring at 70° C. for about 1 hour, and then adding 2.5parts of a water-soluble aliphatic denatured amine and furthercontinuing the stirring for 6 hours.

By isolating the pigment from the aforementioned microcapsule pigmentsuspension by centrifugation, a thermochromic coloring color-memorymicrocapsule pigment having an average particle diameter of 6 μm whichchanges color from blue to colorless was obtained.

Example 3

A thermochromic coloring color-memory microcapsule pigment suspensionwas obtained by uniformly heat-dissolving a thermochromic coloringcolor-memory composition comprising 2.0 parts of3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalideas the component (A), 8.0 parts of 1,1-bis (4′-hydroxyphenyl)-n-decaneas the component (B) and 50.0 parts of 4-benzyloxyphenylethyl myristateas the component (C), emulsifying and dispersing a solution prepared asa wall membrane material by mixing 30.0 parts of an aromatic polyvalentisocyanate prepolymer with 40.0 parts of a co-solvent such thatmicro-droplets were formed in 8% polyvinyl alcohol aqueous solution,continuing the stirring at 70° C. for about 1.5 hours, and then adding2.5 parts of a water-soluble aliphatic denatured amine and furthercontinuing the stirring for 6 hours.

By isolating the pigment from the aforementioned microcapsule pigmentsuspension by centrifugation, a thermochromic coloring color-memorymicrocapsule pigment having an average particle diameter of 4 μm whichchanges color from blue to colorless was obtained.

Example 4

A thermochromic coloring color-memory microcapsule pigment suspensionwas obtained by uniformly heat-dissolving a thermochromic coloringcolor-memory composition comprising 2.0 parts of3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalideas the component (A), 8.0 parts of 1,1-bis (4′-hydroxyphenyl)-n-decaneas the component (B) and 50.0 parts of 4-benzyloxyphenylethyl laurate asthe component (C), emulsifying and dispersing a solution prepared as awall membrane material by mixing 30.0 parts of an aromatic polyvalentisocyanate prepolymer with 40.0 parts of a co-solvent such thatmicro-droplets were formed in 8% polyvinyl alcohol aqueous solution,continuing the stirring at 70° C. for about 1 hour, and then adding 2.5parts of a water-soluble aliphatic denatured amine and furthercontinuing the stirring for 6 hours.

By isolating the pigment from the aforementioned microcapsule pigmentsuspension by centrifugation, a thermochromic coloring color-memorymicrocapsule pigment having an average particle diameter of 4 μm whichchanges color from blue to colorless was obtained.

Example 5

A thermochromic coloring color-memory microcapsule pigment suspensionwas obtained by uniformly heat-dissolving a thermochromic coloringcolor-memory composition comprising 2.0 parts of3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalideas the component (A), 4.0 parts of 2,2-bis(4′-hydroxyphenyl)hexafluoropropane and 4.0 parts of 1,1-bis (4′-hydroxyphenyl)-n-decaneas the component (B) and 50.0 parts of 4-benzyloxyphenylethyl caprate asthe component (C), emulsifying and dispersing a solution prepared as awall membrane material by mixing 30.0 parts of an aromatic polyvalentisocyanate prepolymer with 40.0 parts of a co-solvent such thatmicro-droplets were formed in 8% polyvinyl alcohol aqueous solution,continuing the stirring at 70° C. for about 1 hour, and then adding 2.5parts of a water-soluble aliphatic denatured amine and furthercontinuing the stirring for 6 hours.

By isolating the pigment from the aforementioned microcapsule pigmentsuspension by centrifugation, a thermochromic coloring color-memorymicrocapsule pigment having an average particle diameter of 3 μm whichchanges color from blue to colorless was obtained.

Example 6

A thermochromic coloring color-memory microcapsule pigment suspensionwas obtained by uniformly heat-dissolving a thermochromic coloringcolor-memory composition comprising 2.0 parts of3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalideas the component (A), 4.0 parts of2,2-bis(4′-hydroxyphenyl)hexafluoropropane and 4.0 parts of1,1-bis(4′-hydroxyphenyl)-n-decane as the component (B) and 50.0 partsof 4-benzyloxyphenylethyl caprylate as the component (C), emulsifyingand dispersing a solution prepared as a wall membrane material by mixing30.0 parts of an aromatic polyvalent isocyanate prepolymer with 40.0parts of a co-solvent such that micro-droplets were formed in 8%polyvinyl alcohol aqueous solution, continuing the stirring at 70° C.for about 1 hour, and then adding 2.5 parts of a water-soluble aliphaticdenatured amine and further continuing the stirring for 6 hours.

By isolating the pigment from the aforementioned microcapsule pigmentsuspension by centrifugation, a thermochromic coloring color-memorymicrocapsule pigment having an average particle diameter of 3 μm whichchanges color from blue to colorless was obtained.

Example 7

A thermochromic coloring color-memory microcapsule pigment suspensionwas obtained by uniformly heat-dissolving a thermochromic coloringcolor-memory composition comprising 5.0 parts of2-(2-chloroanilino)-6-di-n-butylaminofluoran as the component (A), 5.0parts of 2,2-bis (4′-hydroxyphenyl) hexafluoropropane and 10.0 parts of1,1-bis (4′-hydroxyphenyl)-n-decane as the component (B) and 50.0 partsof 4-benzyloxyphenylethyl caprate as the component (C), emulsifying anddispersing a solution prepared as a wall membrane material by mixing30.0 parts of an aromatic polyvalent isocyanate prepolymer with 40.0parts of a co-solvent such that micro-droplets were formed in 8%polyvinyl alcohol aqueous solution, continuing the stirring at 70° C.for about 1 hour, and then adding 2.5 parts of a water-soluble aliphaticdenatured amine and further continuing the stirring for 6 hours.

By isolating the pigment from the aforementioned microcapsule pigmentsuspension by centrifugation, a thermochromic coloring color-memorymicrocapsule pigment having an average particle diameter of 2 μm whichchanges color from black to colorless was obtained.

Example 8

A thermochromic coloring color-memory microcapsule pigment suspensionwas obtained by uniformly heat-dissolving a thermochromic coloringcolor-memory composition comprising 2.3 parts of1,3-dimethyl-6-diethylaminofluoran and 0.7 part of1,2-benz-6-(N-ethyl-N-isobutylamino) fluoran as the component (A), 5.0parts of 2,2-bis(4′-hydroxyphenyl) hexafluoropropane and 10.0 parts of1,1-bis (4′-hydroxyphenyl)-n-decane as the component (B) and 50.0 partsof 4-benzyloxyphenylethyl caprate as the component (C), emulsifying anddispersing a solution prepared as a wall membrane material by mixing30.0 parts of an aromatic polyvalent isocyanate prepolymer with 40.0parts of a co-solvent such that micro-droplets were formed in 8%polyvinyl alcohol aqueous solution, continuing the stirring at 70° C.for about 1 hour, and then adding 2.5 parts of a water-soluble aliphaticdenatured amine and further continuing the stirring for 6 hours.

By isolating the pigment from the aforementioned microcapsule pigmentsuspension by centrifugation, a thermochromic coloring color-memorymicrocapsule pigment having an average particle diameter of 2 μm whichchanges color from red to colorless was obtained.

Example 9

A thermochromic coloring color-memory microcapsule pigment suspensionwas obtained by uniformly heat-dissolving a thermochromic coloringcolor-memory composition comprising 2.0 parts of2-(butylamino)-8-(diphenylamino)-4-methylspiro[5H-(1)-benzopyrano[2-3-g]pyrimidine-5,1(3′H)-benzofuran]-3-oneas the component (A), 10.0 parts of5,5′-(1-methylethylidene)bis[1-phenyl-2-ol] as the component (B) and50.0 parts of 4-benzyloxyphenylethyl caprate as the component (C),emulsifying and dispersing a solution prepared as a wall membranematerial by mixing 30.0 parts of an aromatic polyvalent isocyanateprepolymer with 40.0 parts of a co-solvent such that micro-droplets wereformed in 8% polyvinyl alcohol aqueous solution, continuing the stirringat 70° C. for about 1 hour, and then adding 2.5 parts of a water-solublealiphatic denatured amine and further continuing the stirring for 6hours.

By isolating the pigment from the aforementioned microcapsule pigmentsuspension by centrifugation, a thermochromic coloring color-memorymicrocapsule pigment having an average particle diameter of 5 μm whichchanges color from pink to colorless was obtained.

Example 10

A thermochromic coloring color-memory microcapsule pigment suspensionwas obtained by uniformly heat-dissolving a thermochromic coloringcolor-memory composition comprising 2.0 parts of2-(butylamino)-8-(diphenylamino)-4-methylspiro[5H-(1)-benzopyrano[2-3-g]pyrimidine-5,1(3′H)-benzofuran]-3-oneas the component (A), 8.0 parts of4,4′-[1-[4-[1-(4-hydroxy-3-methylphenyl)-1-methylphenyl]-ethylidene]bis[2-methylphenol]as the component (B) and 50.0 parts of 4-benzyloxyphenylethyl caprate asthe component (C), emulsifying and dispersing a solution prepared as awall membrane material by mixing 30.0 parts of an aromatic polyvalentisocyanate prepolymer with 40.0 parts of a co-solvent such thatmicro-droplets were formed in 8% polyvinyl alcohol aqueous solution,continuing the stirring at 70° C. for about 1 hour, and then adding 2.5parts of a water-soluble aliphatic denatured amine and furthercontinuing the stirring for 6 hours.

By isolating the pigment from the aforementioned microcapsule pigmentsuspension by centrifugation, a thermochromic coloring color-memorymicrocapsule pigment having an average particle diameter of 3 μm whichchanges color from pink to colorless was obtained.

Example 11

A thermochromic coloring color-memory microcapsule pigment suspensionwas obtained by uniformly heat-dissolving a thermochromic coloringcolor-memory composition comprising 2.0 parts of2-(butylamino)-8-(diphenylamino)-4-methylspiro[5H-(1)-benzopyrano[2-3-g]pyrimidine-5,1(3′H)-benzofuran]-3-oneas the component (A), 8.0 parts of bis(3-methyl-4-hydroxyphenyl)sulfideas the component (B) and 50.0 parts of 4-benzyloxyphenylethyl caprate asthe component (C), emulsifying and dispersing a solution prepared as awall membrane material by mixing 30.0 parts of an aromatic polyvalentisocyanate prepolymer with 40.0 parts of a co-solvent such thatmicro-droplets were formed in 8% polyvinyl alcohol aqueous solution,continuing the stirring at 70° C. for about 1 hour, and then adding 2.5parts of a water-soluble aliphatic denatured amine and furthercontinuing the stirring for 6 hours.

By isolating the pigment from the aforementioned microcapsule pigmentsuspension by centrifugation, a thermochromic coloring color-memorymicrocapsule pigment having an average particle diameter of 2 μm whichchanges color from pink to colorless was obtained.

Preparation of Measuring Sample

After dissolving 30 parts of the thermochromic coloring color-memorycomposition of Example 1 in methyl ethyl ketone, a filter paper (No. 2filter paper, mfd. by Toyo Roshi Kaisha) was impregnated with thesolution to obtain a measuring sample.

Using a reversible thermal discoloration ink prepared by dispersing 40parts of each of the microcapsule pigment of Examples 2 to 10 inethylene-vinyl acetate emulsion, a circle of a predetermined size(reversible thermal discoloration layer) was printed on a sheet ofwood-free paper by screen printing, thereby obtaining respective testsamples.

Each of the thus obtained test samples was heated and cooled by thefollowing method, and the discoloration behavior was plotted on a graph.

Measurement of Discoloring Temperature

The aforementioned measuring sample was set on a predetermined positionof a color-difference meter (TC-3600 Color-Difference Meter, mfd. byTokyo Denshoku), and the color density at each temperature was measuredby heating and cooling at a rate of 10° C./min with a temperature widthof 100° C.

For example, in the case of Example 1, the sample was heated up to 80°C. at a rate of 10° C./min starting at −20° C. as the measurementstarting temperature, and then again cooled down to −20° C. at a rate of10° C./min. The lightness value at each temperature displayed on thecolor-difference meter was plotted on a graph to prepare the colordensity-temperature curve exemplified in FIG. 1, and each of the valuesof T₁, T₂, T₃, T₄, T_(H), T_(G) and ΔH (line segment HG) was obtained.

The following table shows T₁ (complete coloring temperature), T₂(coloring starting temperature), T₃ (decoloring starting temperature),T₄ (complete decoloring temperature) T_(H) (temperature of middle pointbetween T₁ and T₂; T₁+T₂/2), T_(G) (temperature of middle point betweenT₃ and T₄; T₃+T₄/2) and ΔH (maximum hysteresis width; T_(G) T_(H)) ofthe thermochromic coloring color-memory composition and thermochromiccoloring color-memory microcapsule pigment used in each test sample.

TABLE 1 Thermal discoloration temperature characteristics Example T₁ T₂T₃ T₄ T_(H) T_(G) ΔH 1 −10.0 0.0 45.0 65.0 −5.0 55.0 60.0 2 15.0 30.059.0 78.0 22.5 68.5 46.0 3 16.0 22.0 63.0 75.0 19.0 69.0 50.0 4 −2.0 6.056.0 70.0 2.0 63.0 61.0 5 −14.0 −6.0 48.0 62.0 −10.0 55.0 65.0 6 −24.0−10.0 42.0 55.0 −17.0 48.5 65.5 7 −22.0 −14.0 40.0 58.0 −18.0 49.0 67.08 −20.0 −12.0 36.0 60.0 −16.0 48.0 64.0 9 −14.0 −6.0 32.0 58.0 −10.045.0 55.0 10 −20.0 −8.0 35.0 56.0 −14.0 45.5 59.5 11 −14.0 −9.0 43.061.0 −11.5 52.0 63.5

Application Example 1

A reversible discoloration layer was arranged on the surface of a whitepolyester film (25 μm in thickness) used as the support, by printing itusing an ink prepared by dispersing the thermochromic coloringcolor-memory microcapsule pigment prepared in Example 5 in a vehiclecontaining a binder resin, and the upper side thereof waslaminate-treated with a transparent polyester film of 16 μm in thicknessto obtain a reversible thermal discoloration display.

The aforementioned display was once cooled to 14° C. or lower to effectcolor development of the reversible discoloration layer into acompletely blue state, and then a white reverse letter was formed byprinting it using a thermal transfer printer (product number: S4870,mfd. by Showa Information Systems).

The aforementioned white reverse letter can be observed with the nakedeye so long as the aforementioned display is kept at a temperature offrom −6° C. to 48° C.

Also, the white reverse letter became invisible when the aforementioneddisplay was again cooled to −14° C. or lower thereby allowing thediscoloration layer to develop a color of completely blue state, so thatit was able to use the display repeatedly again and again by forming thewhite reverse letter using the aforementioned thermal transfer printer.

Application Example 2 Preparation of Reversible Thermal DiscolorationInk

A reversible thermal discoloration ink comprising 5.5 parts of thethermochromic coloring color-memory microcapsule pigment prepared inExample 7, 0.33 part of xanthan gum (an agent for providing shearingviscosity reduction), 10 parts of urea, 10 parts of glycerin, 0.6 partof a nonionic system permeability providing agent (trade name: NopcoSW-WET-366, mfd. by San Nopco), 0.1 part of a modified silicone systemantifoaming agent (trade name: Nopco 8034, mfd. by San Nopco), 0.1 partof an anti-fungal agent (trade name: Proxel XL-2, mfd. by Zeneca) and73.37 parts of water was prepared.

Preparation of Writing Implement

A polypropylene pipe having an inner diameter of 4.4 mm was filled bysuction with 0.97 g of the aforementioned ink (after allowing themicrocapsule pigment to develop color by cooling to −22° C. or lower inadvance and then to stand at room temperature) and connected with aball-point pen tip holding a 0.7 mm steel ball inside the tip, via aholder made of a resin.

Next, an ink backflow-preventing matter (liquid plug) containingpolybutene as the main component and having viscoelasticity was filledfrom the rear part of the aforementioned polypropylene pipe, the rearpart of the pipe was further interlocked with a tail plug, a front axlebody and a rear axle body were assembled, a cap was fitted, and thendegassing treatment was carried out by centrifugation, thereby obtaininga reversible thermal discoloration ball-point pen.

In this connection, the apex of the aforementioned cap is mounted with asilicone rubber as a frictional body.

Using the aforementioned ball-point pen, a blue letter (handwriting) wasformed by writing on a sheet of paper.

The aforementioned handwriting was black at room temperature (25° C.),but the letter discolored and became colorless when the letter waserased using the frictional body, and it was able to keep this stateunless cooling to −22° C. or lower.

Meanwhile, in the aforementioned area wherein the letters on the papersurface had been decolored, different letters could be written down byusing the aforementioned ball-point pen.

Moreover, in the area wherein the aforementioned letters on the papersurface were decolored, blue-colored letters can be written down byusing a ball-point pen charged with the thermochromic coloringcolor-memory microcapsule pigment described in Example 6.

Application Example 3 Preparation of Reversible Thermal DiscolorationInk

A reversible thermal discoloration ink comprising 5.5 parts of thethermochromic coloring color-memory microcapsule pigment prepared inExample 11, 0.5 part of a blue dyestuff (C. I. 42090, mfd. by AizenHodogaya), 0.33 part of succinoglycan (an agent for providing shearingviscosity reduction), 10 parts of urea, 10 parts of glycerin, 0.6 partof a nonionic system permeability providing agent (trade name: NopcoSW-WET-366, mfd. by San Nopco), 0.1 part of a modified silicone systemantifoaming agent (trade name: Nopco 8034, mfd. by San Nopco), 0.1 partof an anti-fungal agent (trade name: Proxel XL-2, mfd. by Zeneca) and72.87 parts of water was prepared.

Preparation of Writing Implement

A polypropylene pipe having an inner diameter of 4.4 mm was filled bysuction with 0.97 g of the aforementioned ink (after allowing themicrocapsule pigment to develop color by cooling to −14° C. or less inadvance and then to stand at room temperature) and connected with aball-point pen tip holding a 0.7 mm steel ball inside the tip, via aholder made of a resin.

Next, an ink backflow-preventing matter (liquid plug) containingpolybutene as the main component and having viscoelasticity was filledfrom the rear part of the aforementioned polypropylene pipe, the rearpart of the pipe was further interlocked with a tail plug, a front axlebody and a rear axle body were assembled, a cap was fitted, and thendegassing treatment was carried out by centrifugation, thereby obtaininga reversible thermal discoloration ball-point pen.

In this connection, the apex of the aforementioned cap is mounted with asilicone rubber as a frictional body.

Using the aforementioned ball-point pen, a purple letter (handwriting)was formed by writing on a sheet of paper.

The aforementioned handwriting was purple at room temperature (25° C.),but the letter discolored and became blue when the letter was erasedusing the frictional body, and it was able to keep this state unlesscooling to −22° C. or less.

In this connection, when the aforementioned sheet pf paper was cooled to−22° C. or lower by putting into a refrigerator, the letter showed adiscoloration behavior of again changing to purple, and theaforementioned discoloration behavior was able to be reproducedrepeatedly.

Application Example 4 Preparation of Reversible Thermal DiscolorationInk

A reversible thermal discoloration ink in which the aforementionedmicrocapsule pigment was suspended in a mildly aggregated state wasprepared by making an aqueous medium comprising 5.5 parts of thethermochromic coloring color-memory microcapsule pigment prepared inExample 8, 5.0 parts of glycerin, 0.7 part of an anti-fungal agent(trade name: Proxel XL-2, mfd. by Zeneca) 0.7 part of a silicone systemantifoaming agent (trade name: SN Defoamer 381, mfd. by San Nopco) and80.7 parts of water, into a uniformly dispersed state, and then adding8.0 parts of an aqueous solution containing 5.0 parts of hydroxyethylcellulose (a water-soluble polymer aggregation agent, trade name:Cellosize, mfd. by Union Carbide Japan) to the aforementioned solutionunder a dispersed state while stirring.

Preparation of Writing Implement

A fiber focusing ink occlusion body (porosity, about 80%) prepared bycoating a polyester sliver with a synthetic resin film was impregnatedwith the aforementioned reversible thermal discoloration ink (afterallowing the microcapsule pigment to develop color by cooling to −20° C.or less in advance and then to stand at room temperature), contained inan axle tube and assembled in such a manner that it contacted with aresin processed pen body of polyester fiber (porosity, about 50%)mounted on the front part of the axle tube, and then a cap was fittedthereto, thus obtaining a water paint marking pen.

In this connection, the apex of the aforementioned cap is mounted with asilicone rubber as a frictional body.

By drawing a line using the aforementioned marking pen on a letterprinted on a sheet of paper, it was able to modify the letter in red.

The aforementioned modified part of the letter was red at roomtemperature (25° C.), but the modified part discolored and becamecolorless when erased using the frictional body, and it was able to keepthis state unless cooling to −22° C. or lower.

In this connection, when the aforementioned sheet pf paper was cooled to−22° C. or lower by putting into a refrigerator, the modified partshowed a discoloration behavior of again changing to red, and theaforementioned discoloration behavior was able to be reproducedrepeatedly.

Application Example 5

In a similar manner, a ball-point pen was prepared by using thereversible thermal discoloration ink prepared in Application Example 2(after allowing the microcapsule pigment to lose color by heating to 58°C. or higher in advance and then to stand at room temperature).

When writing in a paper surface is conducted with use of the ballpointpen thus prepared, the handwriting was not visually recognized due toits colorless nature. But by cooling the paper to −22° C. or less, thehandwriting turned black by color development, and this colored statecould be maintained unless the paper is heated to 58° C. or higher.

By way of precaution, when the aforementioned paper surface was heatedto 58° C. or higher, a discoloration behavior that the letters turnedcolorless again was observed. Such discoloration behavior could bereproduced repeatedly.

1. A writing implement comprising: an ink composition that turns from acolored state to a colorless state for the writing implement; and africtional body for erasing a colored writing formed by the inkcomposition, wherein the ink composition comprises a thermochromiccoloring color-memory microcapsule pigment comprising a thermochromiccoloring color-memory composition in a colored state, the thermochromiccoloring color-memory composition comprises a homogeneous solubilizedmixture of (A) an electron donative coloring organic compound, (B) anelectron accepting compound and (C) a reaction medium which controlscolor reactions of the components (A) and (B), a complete decoloringtemperature (T₄) of the thermochromic coloring color-memory compositionis 50° C. or higher and a coloring starting temperature (T₂) ofthermochromic coloring color-memory composition is 10° C. or lowerregarding the color density-temperature curve, and the thermochromiccoloring color-memory composition has color-memory ability at theordinary temperature range.
 2. The writing implement according to claim1, wherein a complete decoloring temperature (T₄) of the thermochromiccoloring color-memory microcapsule pigment is 50° C. to 70° C. and acoloring starting temperature (T₂) of thermochromic coloringcolor-memory microcapsule pigment is 0° C. or lower regarding the colordensity-temperature curve.
 3. The writing implement according to claim1, wherein the writing implement is a ball-point pen.
 4. The writingimplement according to claim 2, wherein the writing implement is aball-point pen.